1. Field of the Invention
The present invention relates to a rotation detector which detects rotation of a rotating machine and a system which is provided with a rotation detector.
2. Description of the Related Art
In the field of servo motors and other rotating machines, it is known to install a rotation detector for obtaining information relating to rotation such as the rotational speed, rotational angle, etc., of the rotating machine (for example, see Japanese Patent Publication No. 2006-10436A). This rotation detector is provided with a moving part which rotates together with an output shaft of the rotating machine and a fixed part which is fastened at the outside of the moving part in the radial direction and which detects a change of a magnetic field which occurs along with rotation of the moving part.
In a conventional rotating machine, the moving part of the rotation detector has been made as a member independent from the rotating part of the rotating machine. Therefore, to secure the performance of the rotation detector, when assembling the rotating machine, precisely positioning the moving part of the rotation detector with respect to the rotating part of the electric motor is necessary. Due to this, it is complicated and improvement of the manufacturing efficiency becomes difficult.
Specifically, the detected part of a rotation detector for which high precision positioning is demanded must be produced separately as an independent ring member separate from the rotation output member which is fastened to the rotating part of the rotating machine. This ring member is fit over the rotation output member when assembling of the rotating machine.
When assembling, the rotation output member which is fastened to the rotating part of the rotating machine is fastened to the rotating part so as to become concentric with the rotating part of the rotating machine, then the ring member at which the detected part is provided is fastened to the rotation output member so as to become concentric with the axis of rotation. Therefore, two steps of precise centering are necessary. Due to this, the assembly process of the rotating machine is complicated and the manufacturing efficiency of the rotating machine is reduced.
The present invention, in consideration of the above problem, has as its object the provision of a rotation detector which can improve the manufacturing efficiency. Further, the present invention has as another object the provision of a system which is provided with a rotating machine and a rotation detector which can improve the manufacturing efficiency.